Jiachen Yin - Academia.edu (original) (raw)

Papers by Jiachen Yin

The Global Positioning System (GPS) is a widely used timing, navigation and positioning system. H... more The Global Positioning System (GPS) is a widely used timing, navigation and positioning system. However, its performance can be significantly degraded by the effects of the various sources of noises due to a highly dynamic multipath environment, signal blockage or attenuation due to ionospheric perturbation. Therefore, the aim of this research is to enhance the GPS signal acquisition and tracking ability to mitigate these effects. Furthermore, it is desirable to provide continuous and consistent positioning information under GPS-denied environments with assistance from multi-sensor data fusion techniques. In this thesis, a novel GPS signal acquisition approach for very dense multipath environments, using a low cost innovative dual polarization patch antenna attached to GPS receiver, is implemented. This reduces the acquisition processing time significantly compared to the conventional serial searching approach. Furthermore, it successfully acquires extra satellites in a dense multipath environment. Furthermore, the GPS signal carrier tracking loop has been considered as one of the most important links in order to demodulate the navigation data frame. An innovative carrier tracking loop is also proposed that comprises two approaches, namely, the adaptive Kalman filter and the adaptive unscented Kalman filter, dynamically integrated with a third order phased locked loop respectively. The proposed two-carrier tracking loops are compared against the conventional carrier tracking loop and the results prove that the proposed approach is more robust and accurate. The carrier tracking performance employing this novel approach is improved, especially in highly dynamic and low CNR environments. Finally, in order to integrate GPS and the sensors, GPS, IMU (inertial measurement unit) and LiDAR are combined for data fusion. A novel line feature extraction and mapping algorithm was designed for LiDAR navigation with a low complexity that resulted in faster feature extraction. This was followed by an innovative integration scheme that combined GPS, IMU and LiDAR, which resulted in continuous, precise positioning data for vehicular communication, even when GPS signals are not available, in a harsh multipath environment.

2016 7th International Conference on Mechanical and Aerospace Engineering (ICMAE), 2016

The amplitude and/or phase fluctuations in the received signal can severely affect the performanc... more The amplitude and/or phase fluctuations in the received signal can severely affect the performance of the Global Positioning System (GPS). These amplitude and phase fluctuations arises when the GPS signal passes through the time-varying electron density irregularities in the ionosphere which can result in loss of lock due to cycle slip in the receiver tracking loop. During cycle slip, the phase jitter serves as an important parameter for updating the receiver tracking loop parameters for efficient tracking either by using a software-based GPS receiver or by hardware modifications. In this paper, a new method of estimating the tracking loop phase jitter is proposed which uses dual frequency based time and spatial variations of total electron content (TEC) at 1 Hz. This method not only involves less computation speed but is also simple to implement compared to the other methods and therefore can significantly improve the performance of the GPS receiver.

2017 European Navigation Conference (ENC)

There has been increasing demand for precise positioning from Global Positioning System (GPS) sat... more There has been increasing demand for precise positioning from Global Positioning System (GPS) satellites, particularly in fading environments that are challenging for the autonomous and semi-autonomous vehicle. GPS signals are right hand circularly polarized (RHCP) however, in dense multipath environments the polarization of a GPS signal may change to become left hand circularly polarized (LHCP). Conventional GPS receivers use RHCP antenna, which reject LHCP signals, and parallel searching acquisition methods that are not sensitive to the resulting weak signals. In vehicular communications, urban environments is a source multipath and weak signals that can lead to GPS lock loss, but obtaining consistent positioning information in urban environments is crucial for vehicular communication. In this paper, we propose a very low-cost dual polarization patch antenna for LHCP GPS signals, but due to the weak signal strength from reflected signals we also propose a modified serial searching acquisition method using a software-based GPS receiver. The experimental results show that using this method we were able to acquire additional satellites that could be used to compensate for the loss of RHCP signals in multipath environments.

Small-scale time-varying electron density irregularities in the ionosphere distort the wave-front... more Small-scale time-varying electron density irregularities in the ionosphere distort the wave-front and result in wavelet interference at the receiver, manifested as variations in amplitude and phase observed at the receiver. Fast phase changes and/or deep amplitude fades can present a considerable problem to the tracking loop of the receiver PLL which can result in a significant positional error. Rapid random fluctuations in amplitude and/or phase of received transionospheric radio signals are termed as ionospheric scintillation, which occurs mainly at low latitudes and in the auroral and polar regions. Generally, in the GPS receiver, fading due to scintillation causes the In-phase and Quadrature-phase components of the received signal to be altered, resulting in large phase jitter in the tracking loop as it attempts to track the perturbed phase. Intense scintillation not only degrades the signal quality but also results in the receiver PLL losing phase lock. In the auroral region, p...

IEEE Access, 2018

The carrier tracking loop in a GPS receiver is considered to be an important process but also a w... more The carrier tracking loop in a GPS receiver is considered to be an important process but also a weak link since the loss of signal lock can occur in a variety of situations. Low carrier-to-noise ratios and highly dynamic environments are common scenarios for a vehicular communication channel when random phase fluctuations in a dynamic environment are common. We propose a novel and robust carrier tracking approach by dynamically integrating an adaptive unscented Kalman filter assisted by a third-order phase lock loop in order to improve the robustness of tracking capability and accuracy in dense and dynamic environments. Experiments are conducted to investigate the tracking performance of the proposed carrier tracking approach and compare it with existing algorithms for generic GPS receiver. Results indicate that the proposed approach has a better performance in tracking capability and tracking accuracy in highly dynamic environments, and the proposed method achieves a better performance on vehicular communication channels. INDEX TERMS Phase lock loop, unscented Kalman filter, software-based GPS receiver, decentralized information sharing.

The Global Positioning System (GPS) is a widely used timing, navigation and positioning system. H... more The Global Positioning System (GPS) is a widely used timing, navigation and positioning system. However, its performance can be significantly degraded by the effects of the various sources of noises due to a highly dynamic multipath environment, signal blockage or attenuation due to ionospheric perturbation. Therefore, the aim of this research is to enhance the GPS signal acquisition and tracking ability to mitigate these effects. Furthermore, it is desirable to provide continuous and consistent positioning information under GPS-denied environments with assistance from multi-sensor data fusion techniques. In this thesis, a novel GPS signal acquisition approach for very dense multipath environments, using a low cost innovative dual polarization patch antenna attached to GPS receiver, is implemented. This reduces the acquisition processing time significantly compared to the conventional serial searching approach. Furthermore, it successfully acquires extra satellites in a dense multipath environment. Furthermore, the GPS signal carrier tracking loop has been considered as one of the most important links in order to demodulate the navigation data frame. An innovative carrier tracking loop is also proposed that comprises two approaches, namely, the adaptive Kalman filter and the adaptive unscented Kalman filter, dynamically integrated with a third order phased locked loop respectively. The proposed two-carrier tracking loops are compared against the conventional carrier tracking loop and the results prove that the proposed approach is more robust and accurate. The carrier tracking performance employing this novel approach is improved, especially in highly dynamic and low CNR environments. Finally, in order to integrate GPS and the sensors, GPS, IMU (inertial measurement unit) and LiDAR are combined for data fusion. A novel line feature extraction and mapping algorithm was designed for LiDAR navigation with a low complexity that resulted in faster feature extraction. This was followed by an innovative integration scheme that combined GPS, IMU and LiDAR, which resulted in continuous, precise positioning data for vehicular communication, even when GPS signals are not available, in a harsh multipath environment.

2016 7th International Conference on Mechanical and Aerospace Engineering (ICMAE), 2016

The amplitude and/or phase fluctuations in the received signal can severely affect the performanc... more The amplitude and/or phase fluctuations in the received signal can severely affect the performance of the Global Positioning System (GPS). These amplitude and phase fluctuations arises when the GPS signal passes through the time-varying electron density irregularities in the ionosphere which can result in loss of lock due to cycle slip in the receiver tracking loop. During cycle slip, the phase jitter serves as an important parameter for updating the receiver tracking loop parameters for efficient tracking either by using a software-based GPS receiver or by hardware modifications. In this paper, a new method of estimating the tracking loop phase jitter is proposed which uses dual frequency based time and spatial variations of total electron content (TEC) at 1 Hz. This method not only involves less computation speed but is also simple to implement compared to the other methods and therefore can significantly improve the performance of the GPS receiver.

2017 European Navigation Conference (ENC)

There has been increasing demand for precise positioning from Global Positioning System (GPS) sat... more There has been increasing demand for precise positioning from Global Positioning System (GPS) satellites, particularly in fading environments that are challenging for the autonomous and semi-autonomous vehicle. GPS signals are right hand circularly polarized (RHCP) however, in dense multipath environments the polarization of a GPS signal may change to become left hand circularly polarized (LHCP). Conventional GPS receivers use RHCP antenna, which reject LHCP signals, and parallel searching acquisition methods that are not sensitive to the resulting weak signals. In vehicular communications, urban environments is a source multipath and weak signals that can lead to GPS lock loss, but obtaining consistent positioning information in urban environments is crucial for vehicular communication. In this paper, we propose a very low-cost dual polarization patch antenna for LHCP GPS signals, but due to the weak signal strength from reflected signals we also propose a modified serial searching acquisition method using a software-based GPS receiver. The experimental results show that using this method we were able to acquire additional satellites that could be used to compensate for the loss of RHCP signals in multipath environments.

Small-scale time-varying electron density irregularities in the ionosphere distort the wave-front... more Small-scale time-varying electron density irregularities in the ionosphere distort the wave-front and result in wavelet interference at the receiver, manifested as variations in amplitude and phase observed at the receiver. Fast phase changes and/or deep amplitude fades can present a considerable problem to the tracking loop of the receiver PLL which can result in a significant positional error. Rapid random fluctuations in amplitude and/or phase of received transionospheric radio signals are termed as ionospheric scintillation, which occurs mainly at low latitudes and in the auroral and polar regions. Generally, in the GPS receiver, fading due to scintillation causes the In-phase and Quadrature-phase components of the received signal to be altered, resulting in large phase jitter in the tracking loop as it attempts to track the perturbed phase. Intense scintillation not only degrades the signal quality but also results in the receiver PLL losing phase lock. In the auroral region, p...

IEEE Access, 2018

The carrier tracking loop in a GPS receiver is considered to be an important process but also a w... more The carrier tracking loop in a GPS receiver is considered to be an important process but also a weak link since the loss of signal lock can occur in a variety of situations. Low carrier-to-noise ratios and highly dynamic environments are common scenarios for a vehicular communication channel when random phase fluctuations in a dynamic environment are common. We propose a novel and robust carrier tracking approach by dynamically integrating an adaptive unscented Kalman filter assisted by a third-order phase lock loop in order to improve the robustness of tracking capability and accuracy in dense and dynamic environments. Experiments are conducted to investigate the tracking performance of the proposed carrier tracking approach and compare it with existing algorithms for generic GPS receiver. Results indicate that the proposed approach has a better performance in tracking capability and tracking accuracy in highly dynamic environments, and the proposed method achieves a better performance on vehicular communication channels. INDEX TERMS Phase lock loop, unscented Kalman filter, software-based GPS receiver, decentralized information sharing.